1. Field of the Invention
This invention relates to a chain hoist, and more particularly to a lever-operated chain hoist equipped with a cargo chain slip-out preventive structure.
2. Description of the Prior Art
Conventionally a lever-operated chain hoist is generally used for handling relatively lightweight objects. In this kind of chain hoist, usually, the operation lever is manipulated manually, and the cargo chain wheel pivoted in the main body frame is rotated, and the link chain wound on this cargo chain wheel is wound up or let off, so that the object is lifted or lowered, or pulled in.
This link chain has a lifting hook provided at its one end, while a stopper ring is linked to the other end, that is, the free end part, as a slip-out preventive member of the link chain.
This stopper ring is intended to prevent the link chain from slipping out of the cargo chain wheel in the main body frame by exceeding the let-off limit, and it is formed in a circular ring shape of which outside diameter is greater than the width of the link of the link chain (for example, as disclosed in the Japanese Utility Model Publication No. 59-91292).
However, the chain hoist in such structure involves the following problems, and its need for improvement has been recognized.
That is, while the link chain is in unloaded state, or if the load applied on the link chain is much smaller than the load bearing capacity of the hoist itself, this stopper ring will not lose is slip-out preventive function.
But when a large load is applied to the link chain, if the free end part of the link chain is unexpectedly retracted in its lifting or lowering work, the stopper ring hits hard against the part in the hoist main body due to this pulling force, and it may be deformed.
As a result, the slip-out preventive function of the stopper ring is lost, and the subsequent chain hoist operation may be disturbed, or if the hook side load is extremely large, the stopper ring may be further deformed, and it may slip out to the load side of the hook from the cargo chain wheel, and such a slip-out event may lead to an unexpected accident in a worst case.